AstraZeneca said a late-stage trial had confirmed the benefit of breast cancer drug Enhertu in patients with an advanced form of the disease who had been previously treated with another therapy.

In a 600-patient trial called DESTINY-Breast02, Enhertu -developed with Japan's Daiichi Sankyo - was compared against a treatment pre-determined by physicians in people with HER2-positive metastatic breast cancer.

The trial evaluated a similar breast cancer patient population as the DESTINY-Breast01 mid-stage trial, which was the basis for initial approvals in Europe and several other countries, AstraZeneca said.

In the DESTINY-Breast02 study, Enhertu met the main goal of statistically significant and clinically meaningful improvement in progression-free survival, a measure of how long a person can live without their disease worsening. The drug also improved overall survival, a key secondary goal.

Detailed results will presented at an upcoming scientific conference.

The HER2 protein contributes to the growth and spread of breast cancer. About one in five patients with breast cancer are considered HER2-positive, according to AstraZeneca.

AstraZeneca's shares were up about 2% on Monday morning, while Daiichi's shares jumped about 15%.

Earlier this month, AstraZeneca and Daiichi secured U.S. approval specifically targeting patients with so-called HER2-low breast cancer, paving the way for billions in sales. 

Enhertu's first approval came in late 2019, as a third-line treatment for breast cancer patients with HER2-positive disease, in the United States.

It has since also secured multiple approvals in other breast cancer settings, as well as forms of lung and gastric cancer.

The drug, which generated sales of $214 million in 2021, belongs to a class of therapies called antibody drug conjugates. It comprises a monoclonal antibody chemically linked to a cell-killing chemotherapy drug.

AstraZeneca secured partial rights to the Daiichi Sankyo compound three years ago in a deal worth up to $6.9 billion.